/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.metadata;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Writable;
import org.apache.nutch.crawl.NutchWritable;

/**
 * This is a simple decorator that adds metadata to any Writable-s that can be
 * serialized by <tt>NutchWritable</tt>. This is useful when data needs to be
 * temporarily enriched during processing, but this temporary metadata doesn't
 * need to be permanently stored after the job is done.
 * 
 * @author Andrzej Bialecki
 */
public class MetaWrapper extends NutchWritable {
	private Metadata metadata;

	public MetaWrapper() {
		super();
		metadata = new Metadata();
	}

	public MetaWrapper(Writable instance, Configuration conf) {
		super(instance);
		metadata = new Metadata();
		setConf(conf);
	}

	public MetaWrapper(Metadata metadata, Writable instance,
			Configuration conf) {
		super(instance);
		if (metadata == null)
			metadata = new Metadata();
		this.metadata = metadata;
		setConf(conf);
	}

	/**
	 * Get all metadata.
	 */
	public Metadata getMetadata() {
		return metadata;
	}

	/**
	 * Add metadata. See {@link Metadata#add(String, String)} for more
	 * information.
	 * 
	 * @param name
	 *            metadata name
	 * @param value
	 *            metadata value
	 */
	public void addMeta(String name, String value) {
		metadata.add(name, value);
	}

	/**
	 * Set metadata. See {@link Metadata#set(String, String)} for more
	 * information.
	 * 
	 * @param name
	 * @param value
	 */
	public void setMeta(String name, String value) {
		metadata.set(name, value);
	}

	/**
	 * Get metadata. See {@link Metadata#get(String)} for more information.
	 * 
	 * @param name
	 * @return metadata value
	 */
	public String getMeta(String name) {
		return metadata.get(name);
	}

	/**
	 * Get multiple metadata. See {@link Metadata#getValues(String)} for more
	 * information.
	 * 
	 * @param name
	 * @return multiple values
	 */
	public String[] getMetaValues(String name) {
		return metadata.getValues(name);
	}

	public void readFields(DataInput in) throws IOException {
		super.readFields(in);
		metadata = new Metadata();
		metadata.readFields(in);
	}

	public void write(DataOutput out) throws IOException {
		super.write(out);
		metadata.write(out);
	}
}